Descriptive analyses of birthweight for single live births in the United States during 1974, using birth certificate information, show that several factors are associated with a high incidence of low birthweight babies. Multivariate analyses were performed to determine correlates of low birthweight. When other factors are held constant, race not white, previous reproductive loss, short interpregnancy interval, outof-wedlock birth, no prenatal care, and maternal age Recent studies of pregnancy outcome have shown a progressive decline of perinatal and infant mortality in all risk categories, including mortality for small preterm infants.' The decline has come at a time of change in many aspects of maternal and infant care: associated factors include improved perinatal services available to both mother and baby, improved care or prevention of specific diseases, and an increased availability of means for spacing or preventing pregnancies.In our study of birth certificate information to evaluate specific factors which increase the risk of a poor pregnancy outcome, we have followed the suggestion of Lewis, et al.,2 and use birthweight distribution as an indicator of pregnancy outcome. Although infant mortality rates remain the primary indicator, low birthweight is also an indicator of considerable interest. Low birthweight is associated with increased perinatal and infant mortality and morbidity, including adverse sequelae such as mental retardation and learning disabilities.Many previous studies have shown that birthweight, in- The study from which the present report has been drawn'4 comprised an examination of United States birth registration data for single live births in 1974. For each race it related the proportion of births which were low birthweight (less than 2501 grams) to risk factors ascertainable from birth certificates. We summarize here the principal findings of that study and report the results of multivariate analyses which examine the risk of having a low birthweight baby by race, maternal age, wedlock status, prenatal care, and maternal education for primigravida, and by these factors and birth order, reproductive history, and interpregnancy interval for multigravida.

Changes in United States infant and perinatal mortality in the period 1965-1973 were exam-ined by race, age at death or length of gestation, and degree of urbanization.The decline of postneonatal mortality rates was greater than the declines of fetal and neonatal mortality rates. Other-than-white infant and fetal mortality rates improved more than the white rates, except in the first day of life. Postneonatal mortality rates improved more in rural than in urban areas, while neonatal and perinatal mortality rates improved more in urban areas than in rural.These improvements in mortality rates have occurred at the same time as changes in medical techniques and the organization and availability of health During the years from 1965 to 1973, the number of births in the United States decreased from 3.8 million in 1965 to 3.1 million in 1973, a 16.6 per cent decline. The decline in births was due to a decrease in age specific birth rates for women of all ages except below 15 years. These changes were accompanied by a decrease in infant and perinatal mortality rates. Infant mortality rates dropped from 24.7 per 1000 live births in 1965 to 17.7 in 1973, and perinatal mortality rates (28 weeks of gestation through 6 days of age) from 27.5 per 1000 live births plus fetal deaths in 1965 to 20.1 in 1973.1,2 This period of rapid decline of mortality rates followed a 15-year period when mortality rates had shown far smaller declines.In this paper, we present new data concerning the changes in infant and perinatal mortality in the period [1965][1966][1967][1968][1969][1970][1971][1972][1973] and selected data on the number of deaths and the mortality rates in various geographic areas. We then use these data to identify target groups for programs to reduce infant and perinatal mortality rates in the United States. A more complete report with data for individual states and cities will be published later. The characteristics analyzed for the study were age-atdeath and duration of pregnancy, race, and degree of urbanization of county of residence. The above characteristics were examined for the United States as a whole, each state, and each city of 250,000 or more population (1970 census).Age-at-death, duration of pregnancy, and race categories are similar to those used by the National Center for Health Statistics. Perinatal mortality rates were calculated using two definitions of the perinatal period: Perinatal I, from 28 weeks of pregnancy through the sixth day of life, and Perinatal II, from 20 weeks of pregnancy through the 27th *These were the latest national data available from the NCHS, and include the 50 states and the District of Columbia.

This study analyzes infant deaths in the United States, 1962 to 1967, by place of residence, to determine to what degree variations in age at death are related to degree of urbanization and race. Results of the study indicate that: (1) after one day of life infant mortality increases progressively as degree of urbanization decreases; (2) the differences between urban and rural death rates are greatest in the posthebdomadal (1 week or older) period; (3) in all age groups at all levels of urbanization, the nonwhite infant is at a marked disadvantage relative to the white infant; (4) the older the infant, the greater the disadvantage for nonwhite infants in rural areas; (5) had the white infant mortality rate prevailed among the nonwhite population over the six-year period from 1962 to 1967 an estimated annual total of 11,597 nonwhite infants would have survived their first year of life; (6) 40% of the excess deaths are in infants under 7 days and 60% in the posthebdomadal period; (7) fetal death rates increase progressively as degree of urbanization decreases, complementing a direct relationship between under 1 day mortality and urbanization resulting in a level trend for perinatal mortality.